Aluminum-Affecting Solidification Behavior, Microstructure, and Tensile Properties in Tin-Zinc Eutectic Alloy

Area of Science:

• Materials Science
• Metallurgy
• Solidification Science

Background:

• Sn-9 wt %Zn is a promising lead-free solder with good properties but suffers from poor corrosion resistance and wettability.
• Aluminum (Al) modification is explored to enhance Sn-Zn alloy performance.
• Understanding solidification parameters and microstructural evolution is crucial for optimizing solder alloys.

Purpose of the Study:

• To investigate the effect of 0.5% and 2.0% Al additions on the solidification, microstructure, mechanical properties, and fracture modes of directionally solidified Sn-9 wt %Zn alloys.
• To analyze how varying cooling rates influence these properties.
• To provide data relevant to industrial soldering conditions.

Main Methods:

• Directional solidification of Sn-9 wt %Zn alloys with Al additions (0.5%, 2.0%).
• Characterization using optical microscopy (OM), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and X-ray diffraction (XRD).
• Tensile testing to evaluate mechanical properties and fracture modes.

Main Results:

• Al additions increased the liquidus temperature and solidification interval while decreasing the eutectic temperature.
• Eutectic cell growth was observed, with refined cellular structures in the Sn-9 wt %Zn-2 wt %Al alloy.
• The Portevin-Le Chatelier (PLC) effect and twinning deformation were noted, influenced by Al content.
• Ultimate tensile strength and elongation decreased with Al addition, but fracture remained ductile.

Conclusions:

• Aluminum modification alters the solidification behavior and microstructure of Sn-9 wt %Zn alloys.
• While Al reduces tensile strength and elongation, it does not compromise the ductile fracture mode.
• The study provides valuable data on the influence of Al and cooling rates, relevant for optimizing lead-free solder applications.